In various areas of medical, chemical, and/or biological technology, it is often desirable to measure the properties of an aqueous solution. For example, it might be desirable to measure pH, temperature, glucose concentration, etc, which typically requires a customized procedure for each type of measurement. Older techniques frequently involve mixing another chemical in the solution and looking for a detectable change, such as a change in color, a change in electrical conductivity, the production of salts, etc.
More recent techniques may use a hydrogel substance that changes its thickness based on the pertinent characteristics of the solution as that solution permeates the hydrogel. If the hydrogel substance is a few millimeters in size, it may take a long time (e.g., hours) for the solution to permeate the hydrogel substance to produce the desired change in thickness. Reducing the size to a few micrometers may reduce the time to permeate and the resulting time to get an accurate reading to a few seconds. However, directly measuring a change in thickness of only a few micrometers may be difficult and expensive.